Flexible sheet-like magnetic discs having a nominal standardized size of about 3.5 inches are widely used in a variety of data storage/retrieval systems. For example, cassettes which include flexible magnetic discs are used in conjunction with personal computers so as to load data and/or programs into the central processing unit of the computer, as well as to store data in an off-site location in a more convenient manner.
When placed into service in a magnetic recording/reproducing apparatus, the magnetic disc (which is accommodated for rotational movement within the interior of the cassette case) is caused to spin relative to a magnetic read/write head by means of a motor-driven spindle coacting with an aperture in the central hub of the magnetic disc. The spindle, moreover, serves to center the magnetic disc relative to the magnetic read/write head so that accurate placement and retrieval of data onto and from the disc will ensue.
The cassette case for the magnetic disc is typically formed with radially elongate (relative to the magnetic disc) access windows--usually on opposing sides of the cassette case so that data magnetically stored on each side of the magnetic disc can be accessed by respective read/write heads associated with the magnetic recording/reproducing apparatus. Protection against inadvertent scratching of the magnetic disc surface and/or accumulation of dust is afforded by means of a relatively thin inverted U-shaped shutter mechanism that is movable along the edge of the cassette case adjacent to the access windows. Thus, the shutter opens and closes the access windows when the disc is placed in service within and removed from, respectively, the magnetic recording/reproducing apparatus. Movement between these opened and closed positions is facilitated by means of a separate spring element (typically formed of a small gauge, but relatively stiff, wire) which exerts a bias force in a direction tending to move the shutter into its closed position.
As can be appreciated, during assembly of flexible magnetic disc cassettes, the separate handling of the spring element necessarily translates into additional labor during cassette manufacturing--hence, increased production costs. Furthermore, handling of the spring element itself is quite tedious due to its relatively small size thereby leading to increased possibility of incorrect positioning of the spring element during assembly of the magnetic disc cassette. Incorrectly positioned spring elements could, in turn, lead to improper performance of the shutter mechanism during use. Accordingly, when incorrectly positioned spring elements are detected during the manufacturing process, the entire cassette is usually rejected--again leading to increased production costs.
According to the present invention, however, shutter elements formed of a plastics material are provided with an integrally molded (unitary) spring element. Thus, separate handling and/or manipulation of the shutter and spring element during assembly of the magnetic disc element is avoided. As a result, the cassettes may be assembled with greater speed and accuracy as compared to conventional cassettes which employ structurally separate shutter mechanisms and spring elements.
The shutter according to the present invention is a relatively thin (e.g., a thickness of between about 0.012" to 0.022", preferably 0.015") inverted U-shaped structure having a base and a pair of depending walls which, like conventional shutters, straddle an upper edge region of the cassette case adjacent to the magnetic disc access windows. The base thus reciprocally moves along the cassette edge so that the depending walls likewise move parallel to respective surfaces of the cassette so that windows defined in the walls are capable of registry with respective ones of the access openings when the shutter is in its opened condition.
An elongate spring element is integrally molded to (i.e., one-piece structure with) the base of the shutter. Most preferably, the integrally molded spring element extends longitudinally outwardly from the base of the shutter and terminates in a free end that coacts with a stop molded into the interior of the cassette. The stop thus serves to positionally fix the free end so that when the shutter is moved in a direction towards the stop, the resiliency of the spring element will translate into a bias force being exerted upon the shutter in an opposite direction. The spring element could, however, be integrally molded into the cassette itself, in which case the stop is associated with the shutter.
Further aspects and advantages of this invention will become more clear after careful consideration is given to the detailed description of the preferred exemplary embodiments thereof which follow.